The present invention relates to a stencil printer or similar printer and more particularly to a printer of the type including a plurality of print drums each for wrapping a particular master therearound and capable of producing, e.g., color printings.
A thermal, digital master masking type of stencil printer is extensively used as a simple, convenient printer. This type of stencil printer includes a thermal head having fine heat generating elements arranged in an array. While a stencil is conveyed in contact with the heat generating elements, current is selectively fed to the elements in the form of pulses in accordance with image data. As a result, the heat generating elements generate heat and form a perforation pattern in the stencil. The perforated stencil, or master, is wrapped around a porous, cylindrical print drum. Ink feeding means is arranged within the print drum so as to feed ink to the inner periphery of the print drum. A press roller or similar pressing means presses a paper sheet against the print drum via the master, causing the ink to ooze out via the porous portion of the print drum and then the perforation pattern of the master. Consequently, the ink is transferred from the print drum to the paper sheet, printing an image on the paper sheet.
A printer of the type including a plurality of print drums has recently been proposed in various forms, as taught in, e.g., Japanese Patent Laid-Open Publication Nos. 10-297074, 11-138961, 11-151852, 11-227309 and 11-208085. In this type of printer, the print drums each are removable from the body of the printer. The print drums are mechanically interconnected and driven to rotate when mounted to the body. To discharge used masters, to make masters or to change colors, the print drums are individually dismounted from the body and again mounted to the body. The problem with this configuration is that all the print drums cannot be mounted to or dismounted from the body at the same time unless a distance between nearby print drums is an integral multiple of the circumferential length of the individual print drum so as to cause the home positions of the print drums to coincide with each other. This, however, makes the entire printer bulky. To make the printer compact, it has been customary to space nearby print drums by a distance shorter than the circumferential length of each print drum while providing an initial phase difference between the nearby print drums.
Assume that the stop position, e.g., home position of the individual print drum is such that a damper mounted on the drum is positioned substantially at the bottom of the drum. Then, when the print drum is left unused over a long period of time, ink to be fed to the drum is apt to soften due to separation and leak via a seam where the damper is positioned. In light of this, the above Laid-Open Publication No. 11-227309 discloses control means capable of obviating such leakage without resorting to any treatment of the print drum and facilitating the mounting and dismounting of the drum as well as the operation of the printer. The control means controls drive means such that the print drum selectively takes a stop position where the damper lies in a preselected angular range upstream or downstream of substantially the bottom of the drum in a direction of rotation of the drum or a mount/dismount position where the damper is positioned substantially at the bottom of the drum. At the mount/dismount position, the print drum can be mounted to or dismounted from the body.
However, the scheme taught in Laid-Open Publication No. 11-227309 has the following problem left unsolved. Assume a stencil printer including a first and a second print drum. Then, in the above document, the stop positions assigned to the print drums each are coincident with the home position different from the mount/dismount position. Therefore, to mount the first drum to the body, the operator of the printer must press a first drum mount/dismount key (75A in the document) so as to cause a mount/dismount drive section assigned to the first print drum to rotate to the mount/dismount position, and then mount the first drum. Likewise, to mount the second drum to the body, the operator must press a second drum mount/dismount key (75B in the document) so as to cause a mount/dismount drive section assigned to the second print drum to rotate to the mount/dismount position, and then mount the second drum.
As stated above, every time the operator desires to mount one print drum to the body, the operator must press the mount/dismount key assigned to the print drum and simply wait until the mount/dismount drive section also assigned to the print drum reaches the mount/dismount position. Such an operation is awkward to perform and wastes time.
Technologies relating to the present invention are also disclosed in, e.g., Japanese Utility Model Laid-Open Publication Nos. 61-85462 and 64-46258, Japanese Patent Laid-Open Publication Nos. 5-229243, 6-71998, 6-293175, 7-1817, 7-17013, 8-39916, 10-109470, 64-18682, 8-39918 and 10-846, and Japanese Patent Application No. 11-184842.
It is therefore an object of the present invention to provide an easy-to-operate printer with a plurality of print drums allowing the operator of the printer to mount the print drums without pressing, e.g., mount/dismount keys each time and thereby saving time.
In accordance with the present invention, a printer includes a body and a plurality of print drums removably mounted to the body for wrapping masters therearound. An initial phase difference is provided between nearby print drums set in the body such that the print drums each can be mounted to the body in a preselected phase. The printer feeds ink to the masters while sequentially pressing a recording medium against the masters to thereby sequentially form images on the recording medium one above the other. An opening/closing member is mounted on the body and movable between a closed position where it covers openings each for mounting and dismounting a particular print drum and an open position where it uncovers the openings. A closed position sensor is responsive to the closed position of the opening/closing member. A drum driving device causes each print drum to rotate. Drum sensors each are assigned to a particular print drum for determining whether or not the print drum is present in the body. Mount/dismount drive sections are mounted on the body, and each is assigned to a particular print drum such that the mount/dismount drive section is connected to the particular print drum, which is to be mounted to the body, and the drum driving device only at a position corresponding to a mount position of the print drum, which corresponds to the preselected phase. Mount position sensors each are response to the position of associated one of the mount/dismount drive sections corresponding to the mount position. A controller controls, in response to a close signal output from the closed position sensor and an absence signal output from the drum sensor assigned to the print drum to be mounted, the drum driving device such that the mount/dismount drive section assigned to the print drum to be mounted takes the position corresponding to the mount position. Also, in response to a mount position signal output from the mount position sensor, the controller controls the drum driving device such that the mount/dismount drive section stops at the position corresponding to the mount position.
Also, in accordance with the present invention, a printer includes a body and a plurality of print drums removably mounted to the body for wrapping masters therearound. An initial phase difference is provided between nearby print drums. The printer feeds ink to the masters while sequentially pressing a recording medium against the masters to thereby sequentially form images on the recording medium one above the other. The print drums each are capable of stopping at a respective home position. Home position sensors each re responsive to the home position of a particular print drum. A home stop priority setting device allows the operator of the printer to select a home stop priority mode, which causes the print drums to stop at respective home positions, neglecting a preselected priority order given to the stop positions of the print drums. An opening/closing member is mounted on the body and movable between a closed position where it covers openings each for mounting and dismounting a particular print drum and an open position where it uncovers the openings. A closed position sensor is responsive to the closed position of the opening/closing member. A drum driving device causes each print drum to rotate. Drum sensors each are assigned to a particular drum for determines whether or not the drum is present in the body. In response to a close signal output from the closed position sensor, presence signals output from the drum sensors and a home stop priority signal output the the home stop priority setting device, the controller controls the drum driving device such that the print drums each take the respective home position, Also, in response to home position signals output from the home position sensors, the controller controls the drum driving device such that the print drums each stop at the respective home position.
Further, in accordance with the present invention, a printer includes a body and a plurality of print drums removably mounted to the body for wrapping masters therearound. An initial phase difference is provided between nearby print drums set in the body such that the print drums each can be dismounted from the print drum in a preselected phase. The printer feeds ink to the masters while sequentially pressing a recording medium against the masters to thereby sequentially form images on the recording medium one above the other. A specified drum stop priority setting device allows the operator of the printer to select a specified drum stop priority mode, which causes any one of the print drums to stop in the preselected phase, neglecting a preselected priority order given to the stop positions of the print drums. An opening/closing member is mounted on the body and movable between a closed position where it covers openings each for mounting and dismounting a particular print drum and an open position where it uncovers the openings. A closed position sensor is responsive to the closed position of the opening/closing member. A drum driving device causes each print drum to rotate. Drum sensors each are assigned to a particular print drum for determining whether or not the drum is present in the body. Mount/dismount position sensors are mounted on the body, and each is assigned to a particular print drum for sensing the preselected phase of the particular print drum. In response to a close signal output from the closed position sensor, presence signals output from the drum sensors and a specified drum stop priority signal output from the specified drum stop priority setting device, the controller controls the drum driving device such that the print drum specified takes the preselected phase. Also, in response to a mount/dismount position signal output from the mount/dismount position sensor, controller controls the drum driving device such that the print drum specified stops at the mount/dismount position.